transparent top bar text color change on scroll

Hi – love your theme and use it pretty exclusively for all sites.

The problem: I am using a transparent header. The phone/info text in the top bar needs to be white in order to be visible enough. The header is sticky. Upon scroll, the header background becomes white, which makes the white phone/info text invisible because there is no contrast.

My question is how to make the phone/info text change color when the page is scrolled, so that the text contrasts with the white header background?

There is an option for this for the Main Menu in Advanced Stying, but not for the top bar elements.

I’m surprised this question has not come up before – I searched but couldn’t find any answers.

i’m using version 4.0.7

Thank you!